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Intact illusory contour formation but equivalently impaired visual shape completion in first- and later-episode schizophrenia.

ABSTRACT: Visual shape completion is a fundamental process that constructs contours and shapes on the basis of the geometric relations between spatially separated edge elements. People with schizophrenia are impaired at distinguishing visually completed shapes, but when does the impairment emerge and how does it evolve with illness duration? The question bears on the debate as to whether cognition declines after illness onset. To address the issue, we tested healthy controls (n = 48), first-episode psychosis patients (n = 23), and chronic schizophrenia patients (n = 49) on a classic psychophysical task in which subjects discriminated the relative orientations of four sectored circles that either formed or did not form visually completed shapes (illusory and fragmented conditions, respectively). Visual shape completion was quantified as the extent to which performance in the illusory condition exceeded that of the fragmented. Half of the trials incorporated wire edge elements, which augment contour salience and improve shape completion. Each patient group exhibited large visual shape completion deficits that could not be explained by differences in age, motivation, or orientation tuning. Patients responded normally to changes in illusory contour salience, indicating that they were forming but not adequately employing such contours for discriminating shapes. Shape completion deficits were most apparent for patients with cognitive disorganization, poor premorbid early adolescent functioning, and normal orientation discrimination. Visual shape completion deficits emerge maximally by the first psychotic episode and arise from higher-level disturbances that are related to premorbid functioning and disorganization. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

SUBMITTER: Keane BP

PROVIDER: S-EPMC6667222 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Intact illusory contour formation but equivalently impaired visual shape completion in first- and later-episode schizophrenia.

Keane Brian P BP Paterno Danielle D Kastner Sabine S Krekelberg Bart B Silverstein Steven M SM

Journal of abnormal psychology 20181022 1

Visual shape completion is a fundamental process that constructs contours and shapes on the basis of the geometric relations between spatially separated edge elements. People with schizophrenia are impaired at distinguishing visually completed shapes, but when does the impairment emerge and how does it evolve with illness duration? The question bears on the debate as to whether cognition declines after illness onset. To address the issue, we tested healthy controls (n = 48), first-episode psycho ...[more]

PMID: 30346202

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Project description:ImportanceSchizophrenia is associated with an increased risk of type 2 diabetes. However, it is not clear whether schizophrenia confers an inherent risk for glucose dysregulation in the absence of the effects of chronic illness and long-term treatment.ObjectiveTo conduct a meta-analysis examining whether individuals with first-episode schizophrenia already exhibit alterations in glucose homeostasis compared with controls.Data sourcesThe EMBASE, MEDLINE, and PsycINFO databases were systematically searched for studies examining measures of glucose homeostasis in antipsychotic-naive individuals with first-episode schizophrenia compared with individuals serving as controls.Study selectionCase-control studies reporting on fasting plasma glucose levels, plasma glucose levels after an oral glucose tolerance test, fasting plasma insulin levels, insulin resistance, and hemoglobin A1c (HbA1c) levels in first-episode antipsychotic-naive individuals with first-episode schizophrenia compared with healthy individuals serving as controls. Two independent investigators selected the studies.Data extractionTwo independent investigators extracted study-level data for a random-effects meta-analysis. Standardized mean differences in fasting plasma glucose levels, plasma glucose levels after an oral glucose tolerance test, fasting plasma insulin levels, insulin resistance, and HbA1c levels were calculated. Sensitivity analyses examining the effect of body mass index, diet and exercise, race/ethnicity, and minimal (≤2 weeks) antipsychotic exposure were performed.Data synthesisOf 3660 citations retrieved, 16 case-control studies comprising 15 samples met inclusion criteria. The overall sample included 731 patients and 614 controls. Fasting plasma glucose levels (Hedges g = 0.20; 95% CI, 0.02 to 0.38; P = .03), plasma glucose levels after an oral glucose tolerance test (Hedges g = 0.61; 95% CI, 0.16 to 1.05; P = .007), fasting plasma insulin levels (Hedges g = 0.41; 95% CI, 0.09 to 0.72; P = .01), and insulin resistance (homeostatic model assessment of insulin resistance) (Hedges g = 0.35; 95% CI, 0.14 to 0.55; P = .001) were all significantly elevated in patients compared with controls. However, HbA1c levels (Hedges g = -0.08; CI, -0.34 to 0.18; P = .55) were not altered in patients compared with controls.Conclusions and relevanceThese findings show that glucose homeostasis is altered from illness onset in schizophrenia, indicating that patients are at increased risk of diabetes as a result. This finding has implications for the monitoring and treatment choice for patients with schizophrenia.

Dataset Information

Intact illusory contour formation but equivalently impaired visual shape completion in first- and later-episode schizophrenia.

Publications

Intact illusory contour formation but equivalently impaired visual shape completion in first- and later-episode schizophrenia.

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